The invention relates to an apparatus for mixing a liquid additive compound with anhydrous ammonia in a vapor phase and a liquid phase to obtain a homogeneous vapor-liquid mixture of the ammonia and liquid additive which can be applied uniformly to soil and other materials.
It is common practice to apply anhydrous ammonia to the soil as a nitrogen fertilizer. Recently, there has been an interest in using the anhydrous ammonia as a vehicle for applying other materials to the soil, such as herbicides, micronutrients, pesticides, and nitrogen stabilizers. Conventional field applicators for applying the ammonia-additive mixture include storage tanks for the ammonia and the additive, a meter regulator for the ammonia, a metering pump for the additive, a flow equalizer manifold having a fixed or variable orifice, and a row of knives which are pulled through the soil at a depth of several inches. In a typical field application, the ammonia is stored in the ammonia tank at about 100-200 psig, at ambient temperature. As the ammonia is metered through the regulator and into the flow equalizer manifold, the pressure drops to about 5-30 psig. Because of the pressure drop through the regulator, most of the ammonia is in the vapor phase when it leaves the regulator and enters the manifold. At this point the ammonia composition is about 90 percent vapor and 10 percent liquid ammonia on a volume basis.
From the meter regulator, the ammonia is carried into the flow equalizer manifold through a connector pipe which connects the regulator with a mixing chamber. The manifold structure includes a distribution chamber, which is a circular chamber having openings in the sidewall therein and a cone-shaped bottom. Flexible applicator hoses connect the chamber wall openings to the soil knives. Inside the chamber, is an orifice sleeve which seats against the chamber wall. This sleeve has openings in it which are smaller than the openings in the chamber wall and the sleeve openings line up with those in the chamber wall.
As the ammonia passes through the connector pipe, the additive compound is injected by the metering pump into the ammonia stream at a point in the pipe which is below the meter regulator and above the flow equalizer manifold. This is referred to as the "downstream injection" of the additive and it is done to prevent chemical breakdown or cross-contamination problems which could occur if the additive was premixed with the ammonia in the ammonia storage tank. However, the liquid additives referred to earlier, for example, nitrapyrin, which is a nitrogen stabilizer, do not readily mix with the vapor-liquid ammonia stream in the downstream injection step.
At least part of the mixing problem is caused by the fact that the centrifugal force tends to move the liquid phases to the outside of the connector pipe, such that they move in a helical flow pattern. This action causes the product stream to separate into three distinct phases, namely, the liquid and vapor phases of the ammonia and the separate liquid phase of the additive. Since the product stream enters the manifold chamber as a three-phase system, there is a very poor distribution of the components through the applicator hoses into the soil knives. The poor distribution is caused by the same centrifuging effect, which causes the heavier liquid phases to be thrown to the outside of the manifold chamber. Therefore, as the liquid travels around the chamber, most of it discharges through the first few openings it crosses in the orifice sleeve and the chamber sidewall. At the same time, the vapor phase of the ammonia leaves the manifold through those openings which offer the least amount of resistance.
From a study of the problem described above, it was concluded that the three-phase stream must be intercepted and homogenized before it enters the flow equalizer manifold, to improve the distribution of the components to the soil knives. In the practice of this invention, a much better distribution of the product to the soil knives is achieved by modifying the conventional field applicator, which is generally used for the field application of ammonia fertilizer compositions which also contain an additive composition, such as a nitrogen stabilizer.